Citizen Cosmotron 7800 is one of the key models from Citizen’s early non-quartz electronic watch era. Introduced in the early 1970s, the Cosmotron series used an electronically-controlled balance system — a technology positioned between traditional mechanical movements and the fully quartz watches that followed. Because it is electronic but not quartz, the model holds a unique place in Citizen’s technical history and is valued by collectors for this transitional mechanism. This reference 7800-870018TA features a clean silver-white dial with thin applied indices, a sharp 1970s faceted case, and the classic Cosmotron “Ω-style” logo at 6 o’clock. The aesthetics remain simple and elegant while clearly representing the early electronic period. The caseback is engraved with the original specifications: CITIZEN ELECTRONIC / PARAWATER / Stainless Steel / 7800-870018TA / serial 11200942. Functions Quick date change via crown push action (date advances when the crown is pressed). Day display in English and Japanese (bilingual). Day adjustment via dial-turning (hand-rotation), typical of the era. The button at 8 o’clock does not activate any function on this unit (several 7800 variations include an unused secondary switch). Size & Wearability The case measures approximately 37.5 mm (excluding crown), offering a strong wrist presence typical of early-70s electronic Citizen designs. A new genuine-leather strap has been installed. A refined and well-balanced example from Citizen’s important non-quartz electronic technology period, representing the company’s experimentation just before the quartz boom. Condition & Notes Running at the time of listing. As a vintage watch, stable operation, accuracy, and water resistance are not guaranteed. The watch will be carefully packed and shipped with tracking for safe delivery.